In recent years, environmental quality standards for phosphor, boron, arsenic and fluorine ions in drinking water, industrial water, industrial wastewater, sewerage treated water and environmental water have been stiffened because of issues in environmental pollution and eutrophication, and a technology for removing them has been demanded.
Phosphor is one of agents causative of the eutrophication, and regulations on a closed area of water have been stiffened. It is also an element which is feared exhausted, and the technology to recover the element from effluent and reuse it has been demanded.
Boron is an element essential for the growth of plant but is known to adversely affect the growth of the plant when an excessive amount is given. Boron is further pointed out to have a possibility of giving an influence on the health of a human body, particularly causing health problems such as the deterioration of a generative function, when being contained in drinking water.
Arsenic is contained in effluent in a non-ferrous metal smelting industry, heated effluent from a geothermal power plant, and underground water in a particular area. It has been known since olden times that arsenic has toxicity. Arsenic tends to accumulate in a living body, and has been considered to cause chronic poisoning, weight reduction, sensory disturbance, liver disturbance, skin deposition and skin cancer.
Fluorine is often contained in effluent discharged from a metal-smelting, glass and electronic material industry. It has been concerned that fluorine may give the influence on a human body, and it has been known that it causes chronic fluorine toxicosis such as mottled tooth, osteosclerosis and thyroid gland disorder, when excessively ingested.
In addition, it is feared that amounts of these emitted hazardous materials will increase with the development of civilization, and the technology for effectively removing them has been demanded.
As for a conventional technology for removing these hazardous materials, a material has been known which has a hydrated ferrite of Ti, Zr or Sn deposited in a three-dimensional network structure made from polyurethane and polyacrylic acid base resin with the use of a suitable binding material (see Patent Document 1). This publicly known adsorbent is a material having the hydrated ferrite deposited on the three-dimensional network structure with the use of the binding material, and accordingly has a defect that the original ion exchange capacity of an adsorption substrate is not sufficiently developed and an adsorption rate decreases, because the used binding material plugs fine pores existing on the surface of the hydrated ferrite which is the adsorption substrate. The adsorbent also has a problem of supporting few amounts of the adsorption substrate in unit volume thereon, because of having a large cavity. The adsorbent further has to be produced with a complicated method.
In addition, the adsorbent is known which makes a hydrated cerium oxide powder supported on a high molecular material (see Non Patent Document 1). The adsorbent is porous, but has a thin film called a skin layer existing on its surface, and according has a defect of decreasing a diffusion rate of a substance to be adsorbed such as phosphor and boron into an absorbing material.
In addition, Patent Document 2 discloses an absorbing material produced by preparing a porous formed article made from cellulose, and making an adsorption substrate formed of hydrated zirconium oxide supported thereon afterward with an impregnation method. The absorbing material has a low binding force of the adsorption substrate because of making the adsorption substrate supported afterward with the impregnation method, and accordingly has a defect that the adsorption substrate flows out while being repeatedly used. In addition, cellulose tends to swell in water, and accordingly has a problem that when the absorbing material is packed in a column and a liquid is passed through it, a formed body is compressed and increases a pressure loss. Furthermore, cellulose has a property of being decomposed by a living organism, so that the absorbing material has a problem of being unsuitable for treating water in which miscellaneous microorganisms coexist such as sewage water, in point of durability in repeated use.    Patent Document 1: JP-A-09-187646    Patent Document 2: JP-A-2002-38038    Non-Patent Document 1: Industry and Environment, September, 1999, pp. 81-85